It is known that, in a large number of aircrafts, including those for civil transport, the engine speeds are controlled individually during a flight (comprising take-off, climbing, cruising, descent and approach phases) by throttle control levers, respectively associated with said engines. Such control levers are able to occupy one position amongst a plurality of positions, including:                an idling or idle position;        a first marked climbing position;        a second marked climbing position, allowing to obtain either a maximum continuous thrust (MCT) speed at the output of the corresponding engine, when at least one of the engines of such an aircraft breaks down, or a flexible take-off (FLEX TO) speed allowing to perform a take-off with a reduced thrust. For performing such a take-off at a FLEX TO speed, the pilot should preliminarily configure specific parameters of said speed. In the absence of configuration of the latter, the MCT speed is applied by default to the corresponding engine upon take off; and        a marked take-off and go-around position corresponding to a speed delivering a maximum take-off or go-around thrust at the output of the engines.        
Moreover, each control lever could occupy an auto-thrust (A/THR) intermediary range of automatic regulation in the corresponding engine speed, by an automatic pilot of the aircraft. Such an intermediary range extends from the idle position to the first climbing position.
However, it happens that the pilot, wishing to take off in a FLEX TO derated take-off speed, positions the control levers in the second climbing position, but forgets to configure the parameters associated with such a FLEX TO speed. In such a case, the MCT speed is applied by default to the engines upon the take-off, what can surprise the pilot (thinking he is taking off at a FLEX TO speed) and lead to take inappropriate actions on the levers with a view to correcting his mistake.
Moreover, should one of the engines of the aircraft break down upon a FLEX TO take-off (the control levers occupy the second climbing position), the pilot should position the control levers in the take-off and go-around position, then position them in the second climbing position, for selecting the MCT speed. Whereas the pilot is already to manage the engine break down, such a reciprocating movement of the control levers, not intuitive for the pilot, is likely to further disturb him.